Studies on the chemistry and properties of diphtheria toxin and modified derivatives of this compound will be carried out for their possible use as cancer chemotherapeutic agents. The nature of the diphtheria toxin receptor will be characterized. Investigations on specific hormones and drug receptors will be carried out. The use and mechanism of action of immobilized drugs will be further investigated. Receptor characterization will be made with the hope to develop specific drugs for specific types of malignancies. Further characterization of the properties and mechanism of action of the pyridine nucleotide transhydrogenases and various NADases will be emphasized. High frequency nmr studies will be utilized in studying structure of "small" enzymes in changing environments as well as binding of substrates and coenzymes to these proteins. Investigations will be initiated on human cancer cells grown in the nude mice and lines of cancer cells will be cloned; investigations will be carried out on specific membrane properties of cancer cells to ascertain whether they are different from those found in normal cells.